It is known in the art to provide an engine top feed fuel injector with a fuel inlet filter mounted within the fuel inlet tube. It is further known to provide a calibration tube which is slidable within the inlet tube for adjusting the force on a solenoid actuated fuel inlet valve and to propose a fuel filter mounted on the outer end of the calibration tube.
In this proposal, the calibration tube is adjusted by a tool which engages the closed outer end of the filter and forces it down with the tube until the desired valve spring force is achieved. The calibration tube is then fixed to the inlet tube by any suitable means to hold the calibration tube in place. The friction force of the tube by itself is inadequate to maintain the set calibration tube position since adjustment of the tube by applying a force to the filter body requires that the sliding force of the calibration tube be limited to an amount which the plastic body of the filter is able to withstand, preferably not more than about two pounds. Also, the low force sliding fit of the calibration tube in the fuel inlet tube allows fuel carrying contaminant particles up to 100 microns in diameter to bypass the filter by passing through clearance spaces between the tubes. It is accordingly desired to provide a calibration tube mounted inlet filter which overcomes the problems of the prior art.